Re: Got 20 minutes?

Howard Ritter

Hi, Roland—

That’s a wonderful degree of mechanical and optical performance! My own 1600AE coming in May is going to be comparatively under-utilized on a portable pier under Northwest Ohio skies, I’m afraid. I think this image of M42 is the flattest I’ve ever seen, in that the outlying regions have been brought out to such a degree without the core swamping the Trapezium. It actually took me a minute to recognize the image and orient myself.

Forgive the gossipy observation, but there’s a jarring inconsistency between the high-end mount, the high-end optics, and the high-end location on the one hand and the rather small imaging chip at the confluence of all of the above. Will the astrograph illuminate a full-frame sensor? 


On Feb27, 2022, at 1802, Roland Christen via <chris1011@...> wrote:

Hi fellow Astronuts,

Since being here on Hawaii island these last 2 weeks we have had incredibly beautiful weather with many clear nights. Which has allowed me to do some software/hardware testing of equipment set up in our observatory. We have 2 scopes set up, a 175 EDF refractor and a 305 F3.8 R-H astrograph. Along with testing, I am also taking lots of images, guided and unguided, short medium and long exposures.  The skies are so dark here that there's almost no light pollution, although the seeing (atmospheric twinkling) can result in FWHM star sizes from 1.5 to 6 arc sec, depending on whether the wind comes off the ocean or over the mountain.

I'm also a bit of a fan of EAA, so I was interested what a beginner could do with nothing but a well polar aligned mount, a good sky model, and a fast scope. A lot of EAA enthusiasts don't bother polar aligning and use stacking software with hundreds of short exposures that inevitably end up taking 20 minutes or so. As such they miss out on a lot of detail that gets lost in the noise of stacking. So, I decided to take a 20 minute exposure and see what the result is. The image is a single 20 minute unguided shot with a QSI-683 CCD chip, H-a filter. Simple Log stretched in MaximDL, auto-flatten background:

This 8300 chip is not of high efficiency, and I could probably get the same result in much less time with a wider field to boot.


Roland Christen

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